1. Field of Invention
The invention relates to a method of inhibiting particle settling in oil-continuous latex polymers, and, more particularly, to a method of stabilizing oil continuous latex polymers by creating a reformable network.
2. Description of the Prior Art
Amine-modified bentonite clays are commonly used as particle stabilizers and rheological modifiers in the cosmetic and paint industries.
A large number of latex polymers are synthesized by an inverse emulsion process. The inverse emulsion process creates a polymer, as discrete particles, suspended in an oil-continuous phase. The particles are prone to settle on aging. This settling is manifested in an oil split at the top of the container and a thick sediment at the bottom.
Bentonite clay has the desirable property of being thixotropic and shear thinning, i.e., it forms a network which is easily destroyed by the application of shear, but then reforms when shear is removed. The problem with "normal" bentonite clay is its incompatibility with hydrocarbon solvents. Amine-modified bentonite clay, or so-called "organo" clays, is compatible with the oil-continuous phase of inverse polymer latices.
Many other materials also exhibit thixotropic, and shear-thinning, properties. Like the organophilic clays, these materials are used primarily in the cosmetic and paint industries. The vast majority of these materials, like starches, poly-acrylates, natural gums and resins, are compatible only in aqueous systems, effectively eliminating them as candidates for use in conjunction with oil continuous latex polymers.
In comparison, there are relatively few oil compatible additives. The literature does not disclose the use of shear-thinning additives as stabilizers for oil-continuous inverse polymer latices.
Desirably, an additive would exist which would overcome the disadvantages of the prior art by being universally compatible, having better processing conditions and achieving a lower overall product viscosity.